To do underwater research or sightseeing, the physical exertion required to swim tires the swimmer and inhibits the ability of the swimmer to remain submersed for extended periods of time. This is due mainly to the additional oxygen needed by a person engaged in a rigorous physical activity, such as swimming. Prior art devices used to preserve one's strength, thereby increasing one's endurance, include propulsion units mounted on boats or sleds. There are many limitations inherent in the aforementioned prior art devices, not the least of which is the inability of the swimmer to use his hands for any task other than to control the propulsion device.
Propulsion units which give the swimmer freedom to use his hands have been developed. One such device disclosed in the patent issued to Keogh-Dwyer, U.S. Pat. No. 2,722,021, is a mechanical power propulsion device to be secured across the chest or back of the user. A bracelet incorporates a control comprising an on/off switch and a dual speed switch. Another prior art device which allows freedom of hand movement is disclosed in the Strader patent, U.S. Pat. No. 3,329,118. Strader invented a propulsion unit having a harness to secure same to the user and further having hand controls attached to the harness.
Despite the convenience in having free hands afforded by the aforementioned patents, the user is still limited by the bulkiness and heaviness of these units leading to the need for buoyancy control means. For example, the aforementioned patent issued to Strader includes a ballast chamber and valves to adjust the buoyancy of the unit. Likewise, the Keogh-Dwyer patent discloses a buoyancy control compartment and control valves. Still another method of buoyancy control well-known in the prior art is the use of weight belts; that is, weights are added or subtracted, as needed, from a belt worn by the user until zero buoyancy is achieved. The additional elements required by any of the aforesaid buoyancy control methods add further to the bulkiness of the units and thus detract from the efficiency of the prior art devices.
More streamlined propulsion units were developed by Bardoni and McCullogh, their inventions being disclosed in U.S. Pat. No. 3,916,814 and U.S. Pat. No. 3,995,578, respectively. Disadvantageously, the power supply and propulsion unit of these prior art inventions comprise unitary devices, thus limiting the versatility and balance of the propulsion assemblies.
Scuba diving creates a type of weightless condition for the diver. Similar to weightlessness experienced, for example in outer space, only a slight force can disrupt the equilibrium of the weightless condition. However, the equilibrium of the scuba diver is in some ways more sensitive due to the need to balance the forces of gravity and bouyancy. If a diver's weight belt is one or two pounds too light, the diver may not be able to submerge, or, may have to exert a great deal of energy swimming down to a depth where compression reduces bouyancy sufficiently to achieve the virtually weightless condition. In achieving proper bouyancy, balance is also vitally important. Any diver who, finding himself a few pounds short for submersion, decides to place an extra pound or two in the pocket of the bouyancy compensator vest will explain how most of the dive was spent trying to prevent rotation caused by unbalanced weight distribution. Similarly, propulsion devices of the prior art have failed to properly allow for even weight distribution. Units placed entirely on the diver's back will cause a loss of balance should the diver attempt to achieve a stationary upright position such as kneeling or standing. Other units, though placed differently, do not allow for sufficient versatility to obtain easy and accurate balance.
Submersible drive means capable of propelling a person underwater, which is streamlined, yet versatile, is desired. Such a device should be easily controllable and generally provide a convenient, efficient method for underwater travel. Additionally, safety features should be incorporated in case of external dangers or internal malfunction.